The present invention relates generally to pad conditioners used to condition polishing pads. The polishing pads can be configured for polishing a variety of materials, including, for example, plastics, glasses, and semiconductor wafers. More particularly, the present invention relates to a pad conditioner with an undulated surface.
During manufacture, semiconductor wafers used in semiconductor fabrication typically undergo numerous processing steps, including deposition, patterning, and etching steps. Details of these manufacturing steps for semiconductor wafers are reported by Tonshoff et al., “Abrasive Machining of Silicon”, published in the Annals of the International Institution for Production Engineering Research, (Volume 39/2/1990), pp. 621–635. In each manufacturing step, it is often necessary or desirable to modify or refine an exposed surface of the wafer in order to prepare the wafer for subsequent fabrication or manufacturing steps.
For example, after a deposition step, the deposited material or layer on a wafer surface generally needs further processing before additional deposition or subsequent processing occurs. In another example, after an etching step, there is often a need to deposit conducting or insulating materials in layers on the etched surface areas of a wafer.
At each step, it is often desirable to achieve a pre-determined level of surface uniformity. It is also desirable to remove surface defects such as pits and scratches. Such surface irregularities may affect the performance of the semiconductor device or create problems during subsequent processing steps.
One method of modifying or refining exposed surfaces of a wafer involves treating the wafer surface with a slurry containing a plurality of loose abrasive particles dispersed in a liquid. Typically, this slurry is applied to a polishing pad and the wafer surface is then moved against the pad in order to remove or take material off of the wafer surface. The slurry may also contain agents that chemically react with the wafer surface. This type of process is commonly referred to as a chemical-mechanical planarization or polishing (CMP) process. A variation of the CMP process employs a fixed abrasive article as the polishing pad, typically with an abrasive-free working fluid.
One problem with CMP is that the process must be carefully monitored in order to achieve a desired wafer surface topography. The use history of the polishing pad, for example, may affect the polishing results. During CMP, the surface of polishing pads for abrasive-slurry type CMP operations become glazed, thus nonreceptive to accommodating or dispensing the abrasive slurry, and otherwise incapable of polishing at a satisfactory rate and uniformity. The polishing pad surface is conditioned so that it is maintained in a proper form for CMP.
Other processes also use polishing pads that require conditioning. For example, polishing pads for glass and plastic polishing may require conditioning. In certain applications, the polishing pads can contain abrasives. U.S. Pat. No. 5,958,794 (Bruxvoort et al.), for example, discloses a fixed abrasive article for polishing wafers.
The polishing pad is conditioned with an abrasive article commonly referred to as a pad conditioner. After repeated conditioning steps, the pad conditioner eventually becomes spent. The pad conditioner becomes spent when it becomes incapable of conditioning the polishing pad at a satisfactory rate and uniformity. Accordingly, the value of a pad conditioner is increased if its useful life can be extended.
After repeated conditioning operations, the polishing pad also becomes spent and needs to be replaced. During replacement of the polishing pad, the CMP apparatus is unavailable and productivity is reduced. A pad conditioner that is too aggressive and abrades the polishing pad too fast can compromise productivity. Most abrasive articles, including pad conditioners, are optimized for one process and one type of workpiece. For example, if a selected pad conditioner is too aggressive and abrades the polishing pad too rapidly, an alternate pad conditioner with a lower cut rate can be used in its place. Managing a supply of various pad conditioner types for various workpieces, however, introduces complexity to the manufacturing environment and increases inventory costs. Accordingly, the value of a pad conditioner is increased if it can be optimized for use in multiple processes and for a variety of workpieces.